1. Field of Invention
This invention relates to a forming method for a seal portion of laminated aluminum tubes, in which the seal portion, one end of the tube, is flattened, melted and formed into a certain shape. This invention also relates to an apparatus for forming a seal portion of laminated aluminum tubes.
2. Description of Related Art
In the past, a seal portion of synthetic resin made tube-type containers, the main body thereof is made of a laminated aluminum tube, is generally formed in such way that, first, an end portion, which comprises a cave and naturally opens to the air, is clamped and flattened by a clamp device. Then a projecting end portion, which is a portion protruded from the clamp device, is heated and melted by a heater. At last, the melted projecting end portion is simply pressed by a pair of sealing metal clamps into a closed flat shape.
According to the prior art described above, the sealing metal clamps are such that they are only capable of pressing the melted projecting end portion, but they cannot control the melted synthetic resin to flow to certain directions. Therefore, the sealing metal clamps according to the prior art cannot form the seal portion into a desired shape.
That is, according to the prior art, the sealing metal clamps only press the melted synthetic resin at the projecting end portion, so that, as shown in FIG. 8, the melted synthetic resin partly protrudes toward the side directions and produces sharp shaped burrs. Users are often bothered by such containers as the burrs scratch his/her fingers or the like and hurt them.
Further, since the sealed portion is formed into a final shape by being simply clamped by the sealing metal clamps, the final shape thereof is limited to such shape as shown in FIG. 8 or the like. And, the sealed portion cannot be formed into any other desired unique shape or any other useful shape which, for example, enables it to comprise a portion such as a hook for placing it on a hanger. The container according to the prior art is not satisfactory enough because the final shape thereof is limited.
Further, in the sealed portion of a tube of the prior art, as the projecting end portion is heated to melt, an aluminum foil layer thereof is partly exposes to the air. Since the projecting end portion is simply pressed and formed into a final shape, the aluminum foil layer 3c is not fully covered with the synthetic resin. It continues to be exposed partially in the air as shown in FIG. 8. The exposed aluminum foil layer corrodes, and the outer periphery of the sealed portion deteriorates, also depreciating the leak resistance of the sealed portion.
Therefore, the object of the present invention is to resolve such problems and to form a sealed portion of laminated aluminum tubes into a desired shape, to form an outer periphery of the sealed portion with an attractive shape, and to cover the aluminum foil layer completely with the synthetic resin.